Radiation control doses are being determined for occult and manifest pulmonary metastases generated by the intraveneous injection of either C3HBA mammary adenocarcinoma or Dunn osteosarcoma in isogeneic C3H/He female mice. Both high LET (accelerated helium ion beams) and conventional low LET (250 kVp X-ray and Co gamma ray) radiation sources are being employed. Combination chemotherapy-radiotherapy treatment protocols are also being tested to determine their effectiveness in the eradication of pulmonary metastasis. The effects of treatment of primary tumors by radiation therapy and/or surgery on the growth of pulmonary metastases are also under investigation. Finally, the effects of breathing a 95% O2 : 5% Co2 atmosphere as compared to breathing air are being studied on mice with macroscopic metastatic lesions being treated by Co.